FXUS63 KOAX 122105
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
305 PM CST SUN DEC 12 2010
.SHORT TERM...TONIGHT THROUGH WEDNESDAY
WITH DEEP UPPER LOW SHIFTING TO THE EAST...FOCUS TURNS TO COLD TEMPS
TONIGHT...THEN INTERMITTENT WEAK DISTURBANCES THIS WEEK. SUBJECTIVE
12Z UPPER AIR ANALYSIS INDICATES UPPER LOW CENTERED NEAR IL/IN
BORDER..WITH 250M HEIGHT FALLS AT 500MB CENTERED IN TN/KY. STRONG
UPPER-LEVEL JET WAS STILL PUSHING IN BEHIND LOW...WITH 155KT IN ND
AND OK AND A WIDE AREA OF 130+KT ACROSS THE CNTRL PLAINS. TEMPS
CERTAINLY HAVE FALLEN AT 850MB...WITH -7C AT KOAX AND -17C UPSTREAM
AT KABR. SURFACE HIGH AT 20Z WAS CENTERED IN ERN ND...WITH RIDGE
AXIS EXTENDING INTO CNTRL NEB. VIS SATELLITE IMAGERY INDICATES SNOW
LINE FROM ROUGHLY BVN TO OLU TO AFK TO FNB...AND COLDER SFC TEMPS
HAVE FOLLOWED THAT LINE PRETTY CLOSELY.
MAIN FORECAST ISSUES ARE COLD TEMPS TONIGHT...POTENTIAL FOR LIGHT
SNOW IN THE NORTH ON MONDAY...AND POTENTIAL WEDNESDAY SYSTEM. FOR
TONIGHT...HAVE NOT CHANGED TEMP FORECAST SIGNIFICANTLY EXCEPT TO
BUMP UP SLIGHTLY IN THE NWRN CWA WHERE CLOUDS MAY FILL IN
OVERNIGHT...AND DECREASE SLIGHTLY IN NERN CWA WHERE DEEPER SNOW
FELL. RIDGE AXIS PASSING OVERHEAD WILL ALLOW TEMPS TO
PLUMMET...TEMPERED BY INCREASING CLOUDS OVERNIGHT. WINDS WILL BE
TOO LIGHT TO CREATE WIND CHILL CONCERNS...THOUGH TEMPS WILL BE
BITTERLY COLD. FAST-MOVING SHORTWAVE IS PROGGED TO DIVE THROUGH THE
NWRLY FLOW TONIGHT AND MONDAY...BRINGING A BRIEF SHOT AT LIGHT
SNOW. WAVE WILL WEAKEN AS IT APPROACHES NEB...AND AM NOT EXPECTING
ACCUMULATING SNOW...BUT DID KEEP SCHC POP IN THE NORTH FOR POTENTIAL
TO GET A MEASURABLE DUSTING. NWRLY FLOW CONTINUES TUESDAY...BUT
LACKING MOISTURE...THINKING ANY WEAK VORTS WILL PRODUCE CLOUDS AT
BEST.
UPPER-LEVEL RIDGING OVER THE ROCKIES IS PROGGED TO SQUASH INTO ZONAL
FLOW BY MIDWEEK AS UPPER LOW COMES ASHORE IN THE PACIFIC NW...WITH
WEAK LOW PROGGED TO MOVE INTO THE DAKOTAS BY LATE WEDNESDAY.
GFS/ECMWF HAVE VARYING DEGREES OF PRECIP COVERAGE AND ALSO VARYING
TIMING...AND EVOLUTION OF SENSIBLE WEATHER ON WEDNESDAY IS LOW
CONFIDENCE. AS MODELS COME INTO AGREEMENT...MAY NEED POPS ADDED FOR
SOME PART OF WEDNESDAY...BUT FOR NOW...HAVE KEPT FORECAST DRY.
.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY
THE LONG TERM PERIOD WILL BEGIN WITH A GENERAL ZONAL FLOW REGIME AS
UPPER LOWS/TROUGHS REMAIN OFF THE NORTHERN WEST AND NEW ENGLAND
COASTS. HOWEVER A STRAY UPPER LOW NOTED BY GFS AND ECMWF IN THE
NORTHERN PLAINS WILL WANDER SOUTHEAST INTO THE GREAT LAKES REGION BY
FRIDAY...DRAGGING COLDER AIR AND LOWERING HEIGHTS BEHIND IN ACROSS
OUR REGION. THUS FORECAST TEMPERATURES WILL HAVE TO BE NUDGED DOWN
JUST A TAD...BUT NO BIG SWINGS ARE ANTICIPATED GIVEN LOW AMPLITUDE
OF THIS SYSTEM.
WILL MAINTAIN A DRY FORECAST THROUGH THE PERIOD...BUT A COUPLE OF
ROUNDS OF LIGHT PRECIP ARE POSSIBLE. ONE IS WEDNESDAY NIGHT AS MID
LEVEL WARM ADVECTION AHEAD OF ADVANCING NORTHERN PLAINS LOW WILL AT
LEAST PRODUCE CLOUDS ACROSS THE REGION. GFS PAINTS A STRIPE OF QPF
CLOSE TO OUR EASTERN CWA WEDNESDAY EVENING...THEN PULLS THIS
NORTHEAST. RELATIVELY DRY LOW LEVELS SHOULD KEEP ANY PRECIP
NEGLIGIBLE HERE. THE NEXT PRECIP CHANCE IS WITH A MINOR WAVE THAT
ROLLS INTO THE REGION SATURDAY OR SUNDAY. GFS AND ECMWF BOTH SHOW
THIS FEATURE...BUT ARE ABOUT 24 HOURS DIFFERENT IN TIMING. TRACK AND
STRENGTH ARE EXTREMELY DIFFICULT TO DISCERN THIS FAR OUT...SO HAVE
KEPT FORECAST DRY FOR NOW.
TEMPERATURES WILL START THE PERIOD IN THE 30S ON THURSDAY...THEN
DROP INTO THE 20S FRIDAY THROUGH SUNDAY ON BACK SIDE OF UPPER LOW
AND UNDER INFLUENCE OF SURFACE CANADIAN HIGH PRESSURE. LOWS NEAR 20
THURSDAY MORNING WILL FALL INTO THE SINGLE DIGITS AND TEENS THROUGH
THE WEEKEND.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
LIMITED LAYER OF VFR CIGS HAD MOVED DOWN MISSOURI VALLEY FROM SD
DURING THE MORNING AND SHOULD GRADUALLY DISSIPATE OR MOVE EAST OF
KOMA AFTER 00Z. INCREASING MID LEVEL CLOUDS EXPECTED AT ALL SITES
AFTER 06Z AS WARM ADVECTION WORKS INTO THE AREA FROM THE WEST.
FORECAST SOUNDINGS SUGGEST KOFK MAY SEE A PERIOD OF MVFR CIGS
12Z-18Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
MAYES/DERGAN/FOBERT